Manufacture of automotive components is continually plagued by seemingly conflicting requirements for engineering materials. For example, various components may be required to possess certain structural characteristics while also being lightweight, durable, aesthetic, and easily manufactured and assembled. Compromises are often made to optimize the most important properties of each component. Alternatively, new materials and processes are continually developed to enhance desirable properties while reducing or eliminating less desirable characteristics.
Plastics have emerged as generally possessing desirable attributes for a variety of automotive applications. Unfortunately, properties which make certain plastics desirable for use in automotive components, such as body panels, fascia, wheel covers, and the like, also result in poor adhesion characteristics for subsequently applied coatings, such as paint or metallic films. The material properties may be altered by introducing additives to enhance adhesion characteristics, varying the coating process, or both.
Once an acceptable material formulation and coating process are developed, it is desirable to implement an appropriate quality assurance procedure to consistently maintain the desirable component characteristics. The quality assurance procedure should identify any nonconforming components as early as possible in the manufacturing process to minimize the expense of time and materials which may be incurred during subsequent manufacturing, or due to customer dissatisfaction manifested in warranty repairs. Preferably, the quality assurance procedure is capable of identifying a particular step or process parameter responsible for a nonconforming component so that prompt corrective action may be instituted whether by the compounder, the part manufacturer (i.e. the molder) or the processor (applying the coating).
Material properties of plastic components may be monitored using any of a number of destructive or nondestructive testing techniques. Destructive testing techniques, such as scanning electron microscopy, are not amenable to use in high-volume manufacturing applications because they are generally time consuming and destroy the part during testing. However, such techniques are useful for gathering various sample data which may be used to investigate material properties or verify on-line testing techniques.
Nondestructive testing of coated or painted surfaces is often performed via visual inspection, either manually or automatically by computer vision/image processing systems. These systems detect defects or flaws which may be present in the coating or on the surface of the substrate. However, changes in plastic material formulation or processing may not be manifested in defects readily apparent from traditional examination of the coating. Undetected changes may then result in subsequent chipping or peeling of the coating from the substrate due to improper adhesion when the component is subjected to impact, abrasion, heat, or the like.